IGCSE Chemistry 0620 Paper 23, Oct/Nov 2025

What happens to the volume of a fixed mass of gas when pressure and temperature are separately increased?

Which gas diffuses most quickly at room temperature and pressure? A ${\text{CH}}_4$ B ${\text{C}}_2{\text{H}}_6$ C $\text{CO}$ D ${\text{SO}}_2$

Which statement defines nucleon number? A It is the total number of protons in the nucleus of an atom. B It is the total number of electrons surrounding the nucleus of an atom. C It is the total number of neutrons in the nucleus of an atom. D It is the total number of protons and neutrons in the nucleus of an atom.

The symbols of four atoms are listed. 1 ${}_6^{12}\text{C}$ 2 ${}_6^{14}\text{C}$ 3 ${}_7^{14}\text{N}$ 4 ${}_{14}^{29}\text{Si}$ Which atoms have more neutrons than protons? A 1 and 2 B 2 and 3 C 2 and 4 D 3 and 4

Which statement describes all positive ions? A Positive ions have more electrons than neutrons. B Positive ions have more protons than neutrons. C Positive ions have more electrons than protons. D Positive ions have more protons than electrons.

A sample of copper has a relative atomic mass of 63.5. What are the relative abundances of the isotopes in this sample of copper? A 25% ${}^{63}\text{Cu}$ and 75% ${}^{65}\text{Cu}$ B 50% ${}^{63}\text{Cu}$ and 50% ${}^{65}\text{Cu}$ C 75% ${}^{63}\text{Cu}$ and 25% ${}^{65}\text{Cu}$ D 90% ${}^{63}\text{Cu}$ and 10% ${}^{65}\text{Cu}$

Which diagram shows the outer shell electron arrangement for a molecule of methanol, ${\text{CH}}_3\text{OH}$?

Rescuers are drilling through fallen rock in order to rescue some people trapped in a cave. The drill needs lubricating from time to time. Four statements are made about the materials used for the drill tip and the lubricant to explain the reasons for their use. 1 Diamond is used for the drill tip as it does not conduct electricity. 2 Diamond is used for the drill tip as it is very hard. 3 Graphite is used as the lubricant as it conducts electricity. 4 Graphite is used as the lubricant as it is soft and slippery. Which statements are correct? A 1 and 3 B 1 and 4 C 2 and 3 D 2 and 4

Which compound has an empirical formula that is the same as its molecular formula? A butane B but-1-ene C butanoic acid D butan-1-ol

Which row identifies the charge on the chromium ion and on the sulfate ion in ${\text{Cr}}_2({\text{SO}}_4{)}_3$?

Which statement describes a saturated solution? A It is a solution that contains the maximum concentration of solute. B It is a solution that contains the maximum amount of solvent. C It is a hydrocarbon that contains both double and single bonds. D It is a hydrocarbon that contains only single bonds.

Calcium carbonate decomposes when heated strongly. $${\text{CaCO}}_3(\text{s})\to \text{CaO}(\text{s})+{\text{CO}}_2(\text{g})$$ How many gaseous molecules are produced when $10.0\text{ g}$ of calcium carbonate is completely decomposed? A $1.00\times {10}^{22}$ B $1.20\times {10}^{23}$ C $6.02\times {10}^{22}$ D $6.02\times {10}^{23}$

Which product is initially obtained at each electrode during the electrolysis of concentrated aqueous sodium chloride?

Molten lead(II) bromide is electrolysed using inert electrodes. Which statement describes the movement of electrons? A from X to Y through the external wire B from Y to X through the external wire C from X to Y through the electrolyte D from Y to X through the electrolyte

In a fuel cell, a fuel is oxidised to produce electricity. Which row describes the fuel and the oxidising agent used?

Which statement about reactions is correct? A A reaction that is vigorous at room temperature has a high activation energy. B If $\mathrm{\Delta }H$ for a reaction is positive, bond making in the formation of the products is endothermic. C In an exothermic reaction, the energy required to break bonds is less than the energy released to make bonds. D Reactions with a positive enthalpy change always transfer thermal energy to the surroundings.

Ethene reacts with hydrogen to form ethane. The bond energies are shown in the table.

What is the enthalpy change for the reaction? A –290 kJ /mol B –120 kJ /mol C +120 kJ /mol D +290 kJ /mol

Zinc reacts with dilute hydrochloric acid. Which statement about the particles in the reaction is correct? A Increasing the concentration of dilute hydrochloric acid increases the collision rate but has no effect on the activation energy. B Increasing the concentration of dilute hydrochloric acid increases the collision rate and the activation energy. C Increasing the temperature of the reaction increases the activation energy. D Increasing the temperature of the reaction causes all collisions to lead to a reaction.

Ethanol is manufactured by the addition of steam to ethene. $${\text{C}}_2{\text{H}}_4(\text{g})+{\text{H}}_2\text{O}(\text{g})\rightleftharpoons {\text{C}}_2{\text{H}}_5\text{OH}(\text{g})$$ The reaction conditions are ${300}^{\circ }\text{C}$ and $60\text{ atm}$. The forward reaction is exothermic. Which rows describe the effect on the equilibrium yield of ${\text{C}}_2{\text{H}}_5\text{OH}$ when the stated change is made?

A 1 and 2 B 1 and 3 C 2 only D 3 only

Which row identifies the conditions used to make sulfur trioxide in the Contact process?

Which statement describes a base? A It reacts with ammonium chloride to produce ammonia gas. B It reacts with calcium carbonate to produce carbon dioxide gas. C It reacts with copper to produce hydrogen gas. D It turns blue litmus red.

The equation shows the reaction between copper and concentrated nitric acid. $$\text{Cu}(\text{s})+4{\text{HNO}}_3(\text{aq})\to \text{Cu}({\text{NO}}_3{)}_2(\text{aq})+2{\text{NO}}_2(\text{g})+2{\text{H}}_2\text{O}(\text{l})$$ Which element is reduced in this reaction? A oxygen B nitrogen C copper D hydrogen

The Periodic Table shows the position of four different elements. Which row is correct?

Dilute acid R and dilute acid S have the same concentration. The same volume of each dilute acid is reacted separately with the same mass of magnesium ribbon. Both reactions are carried out at room temperature and pressure. The volume of hydrogen produced is measured. A graph of the results is shown. Which statement about the reactions is correct? A Acid S reacts faster than acid R. B The final volume of hydrogen produced in each reaction is different. C Acid R is a stronger acid than acid S. D Acid S is a stronger acid than acid R.

Which metal oxide reacts with aqueous sodium hydroxide to form a salt and water? A calcium oxide B copper(II) oxide C sodium oxide D aluminium oxide

Which row identifies a transition element?

Which statement about Group I or Group VII elements is correct? A Group VII elements are monatomic non-metals. B Lithium is more reactive with water than caesium. C The melting point of Group I metals increases down the group. D Potassium bromide reacts with chlorine to produce an orange solution.

Some information about four metals P, Q, R and S is listed. Metal P does not react with dilute hydrochloric acid. Metal Q is more reactive than magnesium. Metal R reacts rapidly with cold water to produce hydrogen. Metal S reacts with dilute hydrochloric acid to produce hydrogen. Which row identifies P, Q, R and S?

Cars are fitted with catalytic converters. Which equation represents a reaction that takes place in a catalytic converter? A ${\text{CO}}_2+{\text{NO}}_2\to \text{CO}+\text{NO}+{\text{O}}_2$ B $2\text{CO}+2\text{NO}\to 2{\text{CO}}_2+{\text{N}}_2$ C ${\text{CO}}_2+{\text{N}}_2\to \text{C}+2\text{NO}$ D $\text{C}+{\text{NO}}_2\to \text{CO}+\text{NO}$

Three statements about greenhouse gases and global warming are listed. 1 A greenhouse gas molecule can absorb and emit thermal energy. 2 The Earth is a source of thermal energy. 3 Thermal energy emitted by a greenhouse gas molecule is sent out in all directions. Which statements are correct? A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Which type of reaction takes place when methane reacts with chlorine in the presence of ultraviolet light? A addition B cracking C polymerisation D substitution

Iron is extracted from iron(III) oxide in the blast furnace. Three steps in the process are listed. 1 Carbon (coke) is completely oxidised. 2 Iron(III) oxide is reduced. 3 Carbon dioxide is reduced to carbon monoxide. What is the correct order of the steps in the extraction of iron? A $1\to 2\to 3$ B $1\to 3\to 2$ C $2\to 1\to 3$ D $3\to 1\to 2$

Three different reactions that occur during the extraction of aluminium from purified bauxite are listed. 1 ${\text{Al}}^{3+}+3{\text{e}}^{-}\to \text{Al}$ 2 $\text{C}+{\text{O}}_2\to {\text{CO}}_2$ 3 $2{\text{O}}^{2-}\to {\text{O}}_2+4{\text{e}}^{-}$ Which reactions occur at the anode? A 1 and 2 B 1 only C 2 and 3 D 3 only

Which statement about aqueous ethanoic acid is correct? A It reacts with magnesium to form oxygen gas. B It reacts with sodium carbonate to form carbon dioxide gas. C It turns red litmus paper blue. D It turns methyl orange yellow.

The diagrams represent four monomers. $${\text{H}}_2\text{N}-\mathrm{\square }-{\text{NH}}_2\text{HOOC}-\mathrm{\square }-{\text{NH}}_2\text{HO}-\mathrm{■}-{\text{NH}}_2\text{HO}-\mathrm{\square }-\text{OH}$$ The monomers each react in a 1 : 1 ratio with the dicarboxylic acid shown. $$\text{HOOC}-\text{/}\mathrm{\square }-\text{COOH}$$ How many of the four monomers shown can react with the dicarboxylic acid to form a polymer? A 1 B 2 C 3 D 4

Propene undergoes addition reactions with bromine, hydrogen and steam. Which structures represent a product of these reactions? A 1 and 3 B 1 and 4 C 2 and 3 D 3 and 4

The structures of four compounds are shown. Which compounds are members of the same homologous series? A 1, 2 and 3 B 1 and 2 only C 1 and 4 D 2 and 4

Which statement about ethanoic acid is correct? A Ethanol is reduced by bacteria to produce ethanoic acid. B Ethanoic acid reacts with magnesium to produce a salt of formula ${\text{CH}}_3\text{COOMg}$. C Ethanoic acid and methanol react in the presence of an acid catalyst to produce ethyl methanoate. D Ethanol reacts with acidified aqueous potassium manganate(VII) to produce ethanoic acid.

Substance X contains one cation. Two tests are completed on aqueous X. test 1 flame test test 2 addition of aqueous sodium hydroxide dropwise and then in excess Which row shows a possible combination of observations for the tests?

A colourless mixture is separated by paper chromatography. The steps below describe the method. These steps are not in the correct order. 1 Remove the chromatography paper from the solvent when the solvent front is near the top of the paper. 2 Place the chromatography paper in the solvent. 3 Spray the chromatography paper with a locating agent. 4 Place a spot of the mixture on the pencil line. 5 Draw a pencil line at the bottom of the chromatography paper. 6 Draw a pencil line to mark the position of the solvent front. What is the correct order for these steps? A $3\to 5\to 6\to 4\to 2\to 1$ B $5\to 4\to 3\to 2\to 1\to 6$ C $3\to 5\to 4\to 1\to 2\to 6$ D $5\to 4\to 2\to 1\to 6\to 3$